1. Field of the Invention
This invention relates to a hermetic container which is useful as a container for display elements including field emission elements, for fluorescent display tubes, or for equivalents.
2. Description of the Related Art
FIG. 2 is a cross sectional view illustrating a field emission display (FED) using field emission elements. A front substrate 101 confronts an opposite substrate 102 so as to be spaced a predetermined distance apart. The gap between the outer fringes of the substrate 100 and the outer fringes of the substrate 101 is sealed with a spacer 102 to construct a container 103. Transparent anode conductors and anodes 104 with fluorescent substance layers are formed on the inner surface of the front substrate 100. Field emission elements 105, or cold cathodes, acting as electron sources are formed on the inner surface of the opposite substrate 101. The field emission elements 105, not shown in detail in FIG. 2, includes cathode conductors formed on the inner surface of the opposite substrate 101, an insulating layer formed over the cathode conductors, gates formed on the insulating layer, and cone emitters each formed on each cathode conductor and in an opening formed in the insulating layer and the gates. When a predetermined anode voltage is applied to the anode 104 and a predetermined voltage is applied to the cathode conductor and the gate in the field emission element 105, electrons are emitted from the tip of the cone emitter to the anode 104, thus glowing the fluorescent substance layer. The glowing of the fluorescent substance layer is viewed through the transparent anode conductor from the outside of the front substrate 100.
In the container 103, supports are often posted between the front substrates 100 and the opposite substrate 101 to maintain the gap between the substrates 100 and 101 to a predetermined small value against the atmospheric pressure.
The container, as shown in FIG. 2, has a getter room 110 that houses a getter for absorbing gases remaining inside the container. The getter room 110 is communicated with the container 103. A getter 111 which is formed of a getter substance filled in a ring cavity is disposed in the getter room 110. An exhaust tube 112 is mounted to the getter room 110 to evacuate air from the container 103. By induction heating the cavity of the getter 111, the getter substance is evaporated to form a getter film over the inner surface of getter room 110.
Generally, in order to fabricate an FED as a flat display element, the gap between the substrates forming the container is often set to a smaller value than the thickness of each substrate. However, the problem is that the whole display element cannot be thinned, in spite of the use of the thin container, because the getter room has a predetermined size to house a getter support. For example, the thickness of the container itself is 2.5 mm or less, but the getter room plus and the exhaust tube protrude 3 to 4 mm ahead.
Since the getter room communicates with the inside of the container at the end portion thereof, the getter can easily absorb gases released from anodes near to the communicating portion. However, it is difficult to effectively absorb gases released from anodes distant from the communicating portion.